Physical Properties.
Substances have physical properties that we can measure, for example, density, melting point, boiling point, solubility, color among others.
Chemical and physical changes.
Substances may undergo these types of changes at different times.
We know a chemical change is occurring when there is a change in a physical property.
In this case, the color of the apple changes. We can also notice that the smell changes. This means that a chemical compound in the apple is converting into another chemical compound.